OKLAHOMA CITY -- Terry L. Nichols began talking almost the moment he surrendered two days after the bombing of the Oklahoma City federal building.

Throughout the afternoon and evening, past midnight and into the days that followed, he laid out a long and rambling story, first declaring that his former Army friend, Timothy J. McVeigh, could not have planted the device that killed 169 people at the site of the Alfred P. Murrah Federal Building.

Then he conceded that it might be possible, but that he himself knew nothing about it. And then finally, he said that Mr. McVeigh could well have been the bomber and that he himself might have "accidentally" played a role.

"I guess you really don't know what your friends will do," he said at one point, distraught and about to collapse into tears.

From dozens of pages of confidential FBI reports obtained this week by the Los Angeles Times comes a detailed account of the man authorities believe did not drive the truck bomb to Oklahoma City for the infamous terrorist strike, but -- almost as importantly -- was an ally, co-strategist and materials supplier for the man who did.

As an indicted conspirator with Mr. McVeigh in the bombing, Mr. Nichols shared a love of guns and a hatred for the federal government. And like Mr. McVeigh, he too faces the death penalty if convicted at his trial next spring. Both men have pleaded not guilty.

The account generally echoes the defense's portrayal of him in recent months -- that he was a friend and fellow military surplus trader with Mr. McVeigh, but not a criminal collaborator.

As a former farmer and junk dealer, the reports suggest, Mr. Nichols, 40, had innocent uses for all of the chemicals and equipment that authorities found on his property and suspect may help link him to the blast.

But in other ways Mr. Nichols' account may add to, rather than allay, suspicions surrounding the two defendants' movements and activities.

In elaborate detail, he outlines for investigators how he and Mr. McVeigh methodically assembled information at gun shows over the past year on how to make bombs from common agricultural compounds.

He recounts some of their travels together, including a rendezvous in downtown Oklahoma City only a few days before the blast.

And the documents reveal the shift in Mr. Nichols' portrayal of his friend's likely culpability.